LONDON Climate change expert Nicholas Stern says he under-estimated the threat from global warming in a major report 18 months ago when he compared the economic risk to the Great Depression of the 1930s.
Latest climate science showed global emissions of planet-heating gases were rising faster and upsetting the climate more than previously thought, Stern said in a Reuters interview on Wednesday.
For example, evidence was growing that the planet's oceans -- an important "sink" -- were increasingly saturated and couldn't absorb as much as previously of the main greenhouse gas carbon dioxide (CO2), he said.
"Emissions are growing much faster than we'd thought, the absorptive capacity of the planet is less than we'd thought, the risks of greenhouse gases are potentially bigger than more cautious estimates, and the speed of climate change seems to be faster," he told Reuters at a conference in London.
Stern said that increasing commitments from some countries such as the European Union to curb greenhouse gases now needed to be translated into action. Policymakers, businesses and environmental pressure groups frequently cite the Stern Review as a blueprint for urgent climate action.
The report predicted that, on current trends, average global temperatures will rise by 2-3 degrees centigrade in the next 50 years or so and could reduce global consumption per head by up to 20 percent, with the poorest nations feeling the most pain.
Some academics said he had over-played the costs of potential future damage from global warming at up to twenty times the cost of fighting the problem now, such as by replacing fossil fuels with more costly renewable power.
Stern said on Wednesday that increasing evidence of the threat from climate change had vindicated his report, published in October 2006.
"People who said I was scaremongering were profoundly wrong," he told the climate change conference organised by industry information provider IHS.
A U.N. panel of scientists, the Intergovernmental Panel on Climate Change (IPCC), writes regular summaries on climate science and last year shared the Nobel Peace prize with former U.S. vice president Al Gore for raising awareness.
Its latest report in 2007 had not taken detailed account of some dangerous threats, including the falling ability of the world's oceans to absorb CO2, because scientists had to be cautious and that evidence was just emerging, the former World Bank chief economist added.
"The IPCC has done a tremendous job but things are moving on," he told Reuters.
"The IPCC's (cautious) approach to this is entirely understandable and sensible, but if you're looking ahead and asking about the risk then you do have to go beyond."
Stern said that to minimise the risks of dangerous climate change global greenhouse gas emissions should halve by mid-century. He said the United States should cut its emissions by up to 90 percent by then.
He was speaking before a senior White House official, speaking on the condition of anonymity, said U.S. President George W. Bush planned on Wednesday to call for a halting of growth in U.S. greenhouse gas emissions by 2025.
(Reporting by Gerard Wynn, Editing by Michael Winfrey)